Field of the Invention
The present invention relates to a power source device.
Description of Related Art
Conventionally, power source control devices such as shown in WO2014/064762 are known.
In the power source control device disclosed in WO2014/064762, electric power generated at a power source is charged in a storage element. A DC-DC convertor converts the power input from an input power feeding line to a prescribed voltage and supplies it to a load connected to an output power feeding line. Exceedance of an input voltage to the first prescribed voltage activates the DC-DC convertor to start power feeding. A power source control unit is connected to the output power feeding line and operates upon receiving power therefrom. The power source control unit controls the power supply to the load while changing operation modes in accordance with the power source energy from the power source. The power source control unit is configured from a microcomputer. The power source control unit is activated upon receiving power supplied from the DC-DC converter, and then operates in a low power-consumption operation mode in which only periodic monitoring of the detected power source energy is performed. The power control unit monitors the power source energy, and starts supplying of power to the load under the condition that the power source energy exceeds the level equivalent to a state where voltage at the input power feeding line reaches the second prescribed voltage higher than the first prescribed voltage.
FIG. 4 is a schematic circuit diagram showing a conventional power source device P1. The conventional power source device P1 includes a storage capacitor P101, a voltage detection circuit P102, a boost circuit P301, a control circuit P302, a switching element P303, input terminals P131, P132, and output terminals P133, P134.
An output terminal P120 of a power generator P100 is connected to one terminal of the storage capacitor P101 via the input terminal P131. An output terminal P120-2 of the power generator P100 is connected to a ground terminal P110 via the input terminal P132. The other terminal of the storage capacitor P101 is connected to a ground terminal P110. One terminal of the storage capacitor P101 is connected to an input terminal P121 of the voltage detection circuit P102, an input terminal P320 of the boost circuit P301, and an input terminal P323 of the control circuit P302.
An output terminal P122 of the voltage detection circuit P102 is connected to an enable terminal P321 of the boost circuit P301. An output terminal P322 of the boost circuit P301 is connected to one terminal of the switching element P303, and a power source terminal P324 of the control circuit P302.
The other terminal of the switching element P303 is connected to an input terminal P127 of the load P105 via the output terminal P133. An input terminal P127-2 of the load P105 is connected to a ground terminal P110 via the output terminal P134. The switching element P303 is controlled by a signal output from the output terminal P325 of the control circuit P302. In the boost circuit P301, the input terminal P320 and the output terminal P322 of the boost circuit P301 are connected via a rectifier such as a Schottky diode.
In the conventional power source device P1 shown in FIG. 4, power generated by the power generator P100 from sunlight, temperature difference, vibration, etc., is charged to the storage capacitor P101. According to detection of the voltage detection circuit P102 that the stored voltage is equal to or greater than the prescribed voltage, the boost circuit P301 converts the storage power to the boosted power.
The switching element P303 controls the boosted power supplied to the load P105. A driving power for the control circuit P302 is supplied from the output terminal P322 of the boost circuit P301. When the stored voltage monitored at the input terminal P323 is equal to or more than the prescribed voltage, the control circuit P302 turns the switching element P303 on.
In the conventional power source device P1 shown in FIG. 4, the control circuit P302 consumes power from the power generator P100. Further, the voltage of the signal (output voltage) supplied from the output terminal P325 to the switching element P303 becomes unstable at the voltage of the power supplied to the power source terminal P324 of the control circuit P302 which is lower than the minimum operation voltage of the control circuit P302. Hence, the switching element P303 becomes weak-on state, and the load 105 also consumes the power from the power generator P100. Accordingly, in a case where the power generated by the power generator P100 is extremely low, the storage power is consumed by the control circuit P302 and the load P105 after the stored voltage rises to a certain level. Then, the stored voltage stops rising.
An object of the present invention is to provide a power source device capable of suppressing power consumption by a load at a low stored voltage without employing a power-consuming control circuit.